Certain power steering systems are convention and described in the pamphlet “ZF-Lenkungen mit Zubehör und Pumpenprogramm” (“ZF Steering Systems With Accessories and Pump Program”), Publication No. G 7000 P-WH 4/97 of ZF Friedrichshafen AG, Geschaeftsbereich Lenkungstechnik (Steering Technology Department). The rotational motion initiated at the steering wheel is transmitted by the steering column and a worm shaft, situated as an extension of the former, with the aid of a continuous bead chain, to a plunger or piston enclosing the worm shaft which is able to have pressure exerted on it from both sides or ends, and the pressure exerted on it is controlled in dependence upon a rotational direction via a control slide that is integrated into the worm shaft and is adjustable as a function of the steering torque applied to it. The bead chain calls for a relatively large annular gap between the plunger guided in the housing, which is axially shiftable along the worm shaft and meshes by its external gearing with a steering sector shaft connected to the steering lever, and the worm shaft that is also supported in the housing, because of the mutual support on the worm shaft and the surrounding working plunger via the bead chain, and this gap has to be sealed so as to separate the working chambers. Sealing is accomplished using an axial seal which, in view of the rotatability of the worm shaft with respect to the working plunger at additional axial shiftability and relatively high pressure differences between the pressure chambers, is exposed to high loads, and all this along with a relatively large annular gap and a high radial prestress of the seal required with respect to the pressure differences to be controlled.
An object of the present invention is to provide a power steering system with respect to the arrangement of the seal to the effect that, with respect to the seal as well as the ring groove and the size of the annular gap's tolerance-insensitive construction, using simple arrangements, a seal may be created between the pressure chambers that may not be sensitive to wear, may be cost-effective and may have a durable service life.